Solenoid magnet



Dec. 22, 1953 s, SNELL 2,663,826

SOLENOID MAGNET Filed 0012. 16, 1951 Fig]; 20 F1750 50 Inventor Maa rice 5. Shell BY wwm Attorneys Patented Dec. 22, 1953 SOLENOID MAGNET Maurice S. Snell, Cranham, England, asslgnor" to Dowty Equipment Limited, Chelte'nham, England Application October 16, 1951, Serial No. 251,457

10 Claims. (Cl. 317--198).

This invention relates to solenoid magnets of the type in which the armature is arranged coaxially with respect to the core. Hitherto it has been the practice to provide a radial air gap which surrounds the armature and separates it magnetically from the solenoid yoke. This air gap though reducing the thrust in the solenoid is nevertheless preferable to the friction that would be present if the armature were a close sliding fit within the guide bore the yoke. The air gap. has to be more than a mere working clearance because any eccentricity in the mounting of the armature would. result in. its tending to move into engagement with one side of the guide bore. To reduce the reluctance of such air gap, the axial dimension of the yoke where it surrounds the armature has usually been extended by hanging or flaring each side of the yoke. The. term air gap is used herein to include an arrangement in which a non-magnetic sleeve serves to centralise the armature- Magnetically such a sleeve has no effect and is therefore the equivalent of a. pure air gap.

The present invention seeks to provide an improved construction of solenoid magnet of the type referred to wherein the air gap is to all intents and purposes eliminated without the introduction of undue friction, whereby a given thrust may be obtained for less ampere turns than has been necessary with known solenoids of the type referred to, or whereby a similar sized solenoid Will afford greater thrust.

The invention is illustrated by way of example in the accompanying drawings, of which:

Figure 1 is a central sectional view of one form of solenoid magnet;

Figure 2 is a central sectional view of another form of solenoid magnet; and

Figure 3 is a central sectional view of a further form of solenoid magnet.

The solenoid magnet in Figure 1 comprises a yoke having a disc-shaped base 3, a core 4 and a housing 5 secured to the base 3 by swaging, while is held winding 6 is disposed in the annular gap between the core 4 and the housing 5. The construction illustrated is more specifically intended for operation of a hydraulic valve and to this end a pair of fixing bolts '1 and 8 are let into the base 3 for securing the latter to the body of a valve.

The armature 9 consists of a disc having one i.

which the inner edges of a plurality or sector- 2 shaped links l3 are received, these links I! in effect forming'part' of the armature. The outer edges of the links l3 fit in a recess l4 in the housing 5, the links 13 being arranged to fit the re ce'ss I4 and the recess in the armature 9 so that they can turn freely through a small angle on either side of a transverse plane. It is preferable to have a fairly large number of links. I3, for ex-' ample twelve or more, so that their outer and inner curved edges will not bind in the respective recesses when they are turned out of the transverse plane. The radial edges of the sectorshaped links 13 are in sufliciently close proximity with each other to provide a, substantially unbroken flux path between the housing 5 and the armature 9.

The. upper end of the housing 5, being reduced in thickness by the formation of the recess I4, is turned outwardly to form a narrow flange 15 on to which the. wider edge of a truncated conical sheet metal cover I6 is secured by rolling or pressing. This cover l6 serves to locate a ring 28 of flexible rubber or the like which retains the outer curved edges of the links l3 in the recess 14, and also to locate a coil spring H which presses on the inner portions of the links I3 to prevent them from vibrating between the flanges H and I2 of the armature 9.

The armature 9 is riveted to a screw threaded bush I8 on which an adjuster head I9 is fitted, while a coil spring 2| is interposed between the head 19 and a flanged collar 22 which rests on a pin 23 slidable in the bush I 8. This pin 23, which is of non-ferrous metal is slidably and centrally mounted in the core 4 and thus serves to guide the movement of the armature 9 towards and away from the core 4.

When the field coil 6 is energised, the armature 9 is attracted towards the core 4 by a force which is greater on account of the floating contact provided between the armature 9 and the yoke (the housing 5) by the links I3, than would be the case using a conventional armature with an air gap separating it from the yoke. The return force on the armature is provided externally by a spring-loaded spindle 24 which is associated with the valve, not shown, and upon which the pin 2;! acts. The attractive force on the armature 9 is applied resiliently to the pin 23 by means of the spring 2 i. and by this means the full force of the solenoid magnet can. be utilized in initiating opening of the valve, while the energy built up in the spring 2| is sufficient to complete the opening of the valve.

The pro-loading of the spring 2! can be ad justed by turning the head I9 on the bush :8 into the required position, in which it is held by the engagement of a spring tag 25 in one of a number of serrations 26 formed on the head !9. A flexible rubber cap 2! is fitted over the housing and the armature may be moved by hand if desired by pressing through this cap 2? on the head I9.

Figure 2 shows in simple form, a cylindrical armature 3| movable axially within the field coil 32 against a shortened core 33 which is attached to the yoke 34. The armature 3| has a circular recess 35, and the yoke 34 a circular recess 35, which receive the inner and outer curved edges respectively of a plurality of links 3?. These links 37 are similar in shape to those in the preceding example but are greater in radial length in proportion to the size of the yoke, and they also in efiect form a part of the armature since they are movable.

The armature 3! has above the recess a wide radial flange 38 to increase the flux between the armature and the links 31. A pin 39 of nonferrous material fixed in the armature 3 l, serves to guide the latter in the yoke 34 and in a cap 40 fitted to the yoke.

In Figure 3, a further alternative construction is shown wherein a number of link-like sectors 41 extend radially inwards from a circular recess 42 in the yoke 43, to a recessed collar 44 of nonferrous material which is fixed on, or integral with a pin 45 mounted slidably in the core 46. The inner portion of the links 4| overlap the face of the core 45 and are preferably arranged to enter into surface contact with it when the solenoid magnet is energised.

It will be realized that the armature 3! in Fig ure 2 and the collar 44 can if desired be mounted resiliently with respect to'their respective pin 39 and 45, in a manner similar to the resilient coupling shown between the armature 8 and pin 23 in Figure 1.

While the solenoid magnets in the preceding examples have been described as suitable for the operation of hydraulic valves, they are in fact suitable in general application where a powerful movement over a relatively short stroke is required.

I claim:

1. A solenoid magnet comprising a spool winding, a core of magnetic material axially disposed within said winding, a yoke also of magnetic material mounting one end of said core and directed lengthwise of said winding, externally thereof, to a termination adjacent the opposite end of the winding, a centrally disposed member located at said opposite end of the winding, an armature including a plurality of oppositely disposed link-like elements each of magnetic material directed radially outwardly from said centrally disposed member to said yoke, pivotal mounting means formed upon the yoke and upon the centrally disposed member, respectively, and engaged with the outer and inner ends of said link-like armature elements for tilting of the latter, and constituting a magnetically conductive path from the yoke to and along said elements, and guide means wherewith said centrally disposed member is operatively engaged, to constrain said member to movement only axially of the winding, towards and from the core.

2. A solenoid magnet comprising a spool winding, a core of magnetic material axially disposed within said winding, a yoke also of magnetic material mounting one end of said core and directed lengthwise of said winding, externally thereof, to

4 a termination adjacent the opposite end of the winding, an armature of magnetic material centrally disposed adjacent that end of the core which is opposite its yoke-mounted end, means guiding the armature for movement axially of and towards and from the core, a plurality of link-like elements of magnetic material directed radially from the armature to the yoke, and means forming a pivotal mount upon the yoke for the outer ends of said link-like elements, and upon the armature for their inner ends.

3. A solenoid magnet as in claim 1, in which said central member is of magnetic material and constitutes the principal component of the armature.

4. A solenoid magnet as in claim 1, wherein the yoke surrounds the winding and the link-like elements radiate in all directions from the centrally disposed member to the yoke.

5. A solenoid magnet as in claim 3, wherein said central member is formed with a radial flange which overlaps a substantial portion of each linklike part and is adapted thereby to increase the magnetic flux between said centrally disposed member and said link-like parts.

6. A solenoid magnet as in claim 5, wherein said centrally disposed member comprises a disc from which said radial flange projects in substantial contiguity with one face of said disc.

7. A solenoid magnet as in claim 2, wherein the yoke is formed as a generally cylindrical housing surrounding the winding, and the linklike elements radiate in all directions from the armature to the yoke, and are complementally sector-shaped, with their radial edges adjoining.

8. A solenoid magnet as in claim 7, including resilient means arranged to press axially upon the several link-like elements, to minimize vibration of the latter relative to said yoke and said armature.

9. A solenoid magnet as in claim 2, including a pin guided in the core for axial movement, and projecting through the armature to constitute the guiding means for the latters axial movement, but itself movable axially relative to the armature, and spring means interposed between said armature and said pin.

10. A solenoid magnet comprising an openended cylindrical yoke of magnetic material circumferentially grooved interiorly about its open I end, a field winding, disposed axially within said yoke, a core disposed within the axis of said winding, a circumferentially grooved central member located axially adjacent the end of said winding, at the open end of the yoke, a plurality of complementally sector-shaped elements collectively constituting a centrally apertured armature disk, formed of magnetic material and seated at their axially inner ends within the groove of said central member, and at their outer circumferential ends within the yokes groove, to overlie the open end of theyoke and winding, and means guiding said central member for movement axially of the core, for approach or recession of said central member and armature elements by hinging movement or each of the latter in the respective grooves.

MAURICE S. I SNELL.

References Cited in the file of this patent UNITED STATES PATENTS 

